java 大小写转换及数组转换字符

java 大小写转换及数组转换字符

public class mainclass {

  public static void main(string[] arg) {
    char[] ch = {'a','b','c','d'};
    system.out.println(string.valueof(ch));  

  }
}

大写转换小写

public class main {

  public static void main(string[] args) {
    string str = "this is a test";

    str = str.tolowercase();

    system.out.println(str);
  }
}
//this is a test

小写转换大写

public class main {
   
    public static void main(string[] args) {
       
        string str = "this is a test";
       
        str = str.touppercase();
       
        system.out.println(str);
    }
}
//this is a test